It is well known that liquid fuels contain components that can degrade during engine operation and form deposits. Such deposits can lead to incomplete combustion of the fuel resulting in higher emissions and poorer fuel economy. Detergents are well known additives in liquid fuels to help minimize deposit formation. However, as the dynamics and mechanics of an engine continually advance, the requirements of the fuels and additives must evolve to keep up with these engine advancements. For example, today's engines have injector system that have smaller tolerances and operate at higher pressure to enhance fuel spray to the compression or combustion chamber. Deposit prevention and reduction have become critical to optimal operation, and therefore there is a need for new detergents capable of providing acceptable performance in a liquid fuel to promote optimal engine operation.
Furthermore, there is a dramatic difference between indirect fuel injected diesel engines, and more modern high pressure common rail (HPCR), direct fuel injected diesel engines. Also, low sulfur diesel fuels and ultra low sulfur diesel fuels are now common in the marketplace for such engines. A “low sulfur” diesel fuel means a fuel having a sulfur content of 500 ppm by weight or less based on a total weight of the fuel. An “ultra low sulfur” diesel fuel (ULSD) means a fuel having a sulfur content of 15 ppm by weight or less based on a total weight of the fuel. Fuel injectors in an HPCR engine perform at much higher pressures and temperatures compared to older style engines and fuel injection systems. The combination of low sulfur or ULSD and HPCR engines have resulted in a change to the type of injector deposits and frequency of formation of injector deposits now being found in the marketplace.
Hence, fuel compositions for direct fuel injected engines often produce undesirable deposits on the internal engine surfaces and fuel filters. Accordingly, improved compositions that can prevent deposit build up, maintaining “as new” cleanliness for the vehicle life are desired. Ideally, the same composition that can clean up dirty fuel injectors, restoring performance to the previous “as new” condition, would be equally desirable and valuable in the attempt to reduce air borne exhaust emissions and to improve the power performance of the engines.
It is known to use polyisobutenyl succinimide (PIBSI)-derived quaternary ammonium salt detergents as additives in fuel compositions to promote optimal engine operation, for example, increased fuel economy, better vehicle drivability, reduced emissions and less engine maintenance by reducing, minimizing and controlling deposit formation. Such quaternized detergents are typically derived from PIBSI compounds that have pendant tertiary amine sites that can be alkylated, i.e. quaternized, by hydrocarbyl epoxides, such as propylene oxide. Examples of such reactions and reaction products are included in U.S. Pat. No. 8,147,569 and U.S. Publication No. 2012/0138004.
A new improved class of quaternary ammonium salt detergents derived from polyisobutenyl succinamides and/or esters have also been disclosed. Such additives are claimed to be more thermally stable than the PIBSI-derived quaternary ammonium detergents and may be manufactured by a less energy-intensive process.
Quaternary ammonium salts detergents often require the use of flammable and dangerous epoxides such as propylene oxide and further require the use of specialized and expensive pressure vessels for their production. The alkoxylation step requires a carboxylic acid as proton donor. The resulting carboxylate may lead to deposit formation and other issues related to carboxylate salts being present in the additive and fuel.
In addition, the polyisobutenyl succinamide and/or ester intermediates tend to be very viscous and difficult to handle during the manufacturing process. The reaction products often contain varying amounts of polyisobutenyl succinimides rendering it difficult to charge a correct amount of epoxide and or acid to the reaction mixture.
In addition, the detergency performance may still need improvement, particularly in fuels containing bio-diesel components.
The present disclosure relates to a class of more effective quaternary ammonium detergents which may be produced by the reaction of a tertiary amine with glycidol, glycidyl ether, and glycidyl ester. In general the substituent group of the glycidyl epoxide has less than five carbon atoms per hetero atom. Such epoxides are readily available in large quantities and require no special pressure reactor for handling.
In accordance with the disclosure, exemplary embodiments provide a fuel soluble additive and its preparation for a diesel engine, a fuel containing the additive, a fuel additive concentrate, a method for improving performance of fuel injectors and a method for cleaning fuel injectors for a diesel engine. The fuel additive includes a quaternary ammonium salt derived from the reaction of (a) a hydrocarbyl amine containing at least one tertiary amino group, (b) an epoxide compound selected from a glycidol, a glycidyl ether, glycidyl ester, polyglycidyl ether, a polyglycidyl ester, and combinations thereof, wherein the substituents of the glycidyl group have, on average, less than five carbon atoms per hetero atom, and (c) optionally a proton donor. The fuel additive concentrate comprises the fuel additive and one or more components and/or solvents.
Another embodiment of the disclosure provides a method of improving the injector performance of a direct fuel injected diesel engine. The method includes operating the engine on a diesel fuel composition containing a major amount of diesel fuel and from about 5 to about 200 ppm by weight based on a total weight of the fuel composition of a quaternary ammonium salt derived from (a) a hydrocarbyl amine containing at least one tertiary amino group, (b) an epoxide compound selected from a glycidol, a glycidyl ether, glycidyl ester, polyglycidyl ether, a polyglycidyl ester, and combinations thereof, wherein the substituents of the glycidyl group have, on average, less than five carbon atoms per hetero atom, and (c) optionally a proton donor.
In another embodiment is provided a fuel soluble additive for a fuel injected diesel engine comprising a quaternary ammonium salt derived from combining (a) a hydrocarbyl amine containing at least one tertiary amino group and (b) an epoxide compound selected from a glycidol, a glycidyl ether, glycidyl ester, polyglycidyl ether, a polyglycidyl ester, and combinations thereof, wherein the substituents of the glycidyl group have, on average, less than five carbon atoms per hetero atom, and (c) optionally a proton donor.
A further embodiment of the disclosure provides a method of operating a direct fuel injected diesel engine. The method includes combusting in the engine a fuel composition containing a major amount of fuel and from about 5 to about 200 ppm by weight based on a total weight of the fuel composition of a quaternary ammonium salt derived from (a) a hydrocarbyl amine containing at least one tertiary amino group (b) an epoxide compound selected from a glycidol, a glycidyl ether, glycidyl ester, polyglycidyl ether, a polyglycidyl ester, and combinations thereof, wherein the substituents of the glycidyl group have, on average, less than five carbon atoms per hetero atom, and (c) optionally a proton donor.
An advantage of the fuel additive described herein is that the additive may not only reduce the amount of deposits forming on fuel injectors, but the additive may also be effective to clean up dirty fuel injectors sufficient to provide improved power recovery to the engine.
Additional embodiments and advantages of the disclosure will be set forth in part in the detailed description which follows, and/or can be learned by practice of the disclosure. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.